Credit: Matt West

Twenty-three games to go, which in the life of an NBA season is a closing sprint.

But as Al Horford admitted after a 10-point loss to the Clippers last Wednesday, when the Celtics gave up a season-high 129 points, they have lost their momentum.

In the absence of Marcus Smart — who is expected to return soon from a hand injury — the Celtics have gone decidedly soft.

“Now we can move on. Now we can shift our focus back on what we need to do, and for our group we need to really tighten up on the defensive end, like I keep harping,” Horford said. “The reason we were winning was defense and rebounding.”

President of Basketball Operations Danny Ainge is still trying to score a shooter in the buyout market, where the options look rather limited right now. Once recently signed Greg Monroe gets comfortable, the second unit will be better-equipped to score.

At the moment, the Celtics don’t begin the stretch run with any semblance of juice.

Here are midseason grades, even if this NBA All-Star break came well after the season’s midpoint.

ARON BAYNES: C

CENTER

5.7 ppg, 5.3 rpg, .461 FG

His presence upgraded the Celtics almost immediately on defense. In terms of rebounding and defensive paint presence, Baynes has been a notable upgrade. But his offense has receded to the point where, save for a couple of recent performances, his attempts to finish have been excruciating.

JAYLEN BROWN: B

FORWARD/GUARD

14 ppg, 5.4 rpg, 1.6 apg, .456 FG, .378 3-pt.

The Rising Stars Challenge was a nice showcase for Brown, who was the most electrifying player on the floor while scoring 35 points with a mix of dunks and 3-pointers. Back to the real stuff, he needs to become a better finisher at the rim under more contested conditions. He’s a work in progress, too, as a defender who wants to take on all the big names.

AL HORFORD: C

POWER FORWARD/CENTER

13.3 ppg, 7.7 rpg, 5.1 apg, 1.1 bpg, .508 FG, .436 3-pt.

He probably will spend the rest of his career shooting better than his lifetime 3-point average (.368), as he is once again doing this season. But he’s slipped since the new year in many aspects of the game, save for his playmaking and ability to guard anyone on the floor.

KYRIE IRVING: A

POINT GUARD

24.7 ppg, 5.0 apg, .486 FG, .397 3-pt., 1.0 spg

Perhaps it was predictable, but Irving finds himself in much the same position as Isaiah Thomas with the Celtics. He’s often the only reliable option. Save for the team’s recent 3-0 surge when he was out with a bruised quad, there’s a noticeable offensive drain when he’s off the floor.

SHANE LARKIN: B

POINT GUARD

.382 FG, .347 3-pt.

Larkin is already a favorite of coach Brad Stevens because of an ability to change the pace of a game. Responsible for a number of turnarounds by the team, albeit with jump shot that runs hot or cold. An energizing presence with the second unit. Expected to return from sore knee this week, the Celtics miss him more than anticipated.

MARCUS MORRIS: B-minus

FORWARD

12.2 ppg, 5.4 rpg, .416 FG, .370 3-pt.

Danny Ainge said he was a scorer, and sure enough, Morris has been one of the Celtics’ few steady options off the bench, and occasionally as a starter when the coach goes small. Shot selection can be a little wild, but he’s certainly not the only one on this team.

ABDEL NADER: B

GUARD/FORWARD

.346 FG, .356 3-pt.

Great example of what Stevens wants out of his bench players — the ability to have an impact despite long stretches of inactivity. A 3-and-D type who can survive in this league.

SEMI OJELEYE: B

POWER FORWARD

.308 FG, .290 3-pt.

Speaking of 3-and-D, Ojeleye has a clear path in this league, just disregard those shooting numbers for now. The rookie’s greatest asset right now is his uncommon combination of strength and lateral ability. Big enough to guard size, and quick enough to pick up point guards.

TERRY ROZIER: C

POINT GUARD

10.1 ppg, 2.4 apg, .393 FG, .374 3-pt.

Rozier had a triple-double in one game and a career-high 31 points in another during Irving’s recent three-game absence. He scored 18 his first game back to coming off the bench, and has been inconsistent ever since. The consistency he brought in his small sample size as a starter needs to parlay to his work with the second unit.

MARCUS SMART: C

GUARD

10.1 ppg, 5.7 rpg, .357 FG, .299 3-pt.

The hand injury he suffered punching a picture frame in a hotel room, hurt his team significantly. Enough to require a talking to from management. The Celtics are clearly a softer bunch without Smart, who may change more games with his rugged hustle and defense than any other wing player in the league. For those praying his shooting improves, he is close to his career averages.

JAYSON TATUM: B

FORWARD

13.5 ppg, .475 FG, .427 3-pt.

Hard to say how much the swollen knuckle on his shooting hand is affecting his shot. Since dislocating the joint in late December, his numbers have dropped. That doesn’t take away from the fact that Tatum has lived up to all projections. The Celtics are strapped enough offensively, and have come to depend on him so much in Gordon Hayward’s absence. They need Tatum to climb over the recent wall he’s encountered.

DANIEL THEIS: B

POWER FORWARD/CENTER

5.2 ppg, 4.2 rpg, .522 FG

A surprise to all but the Celtics personnel staff that believed he was ready to make the jump from Germany to the NBA. Has terrific defensive presence and above-average ability to drive to the rim out of the pick-and-roll — a skill that gets rewarded on this team.

GUERSCHON YABUSELE: C

POWER FORWARD/CENTER

5.0 mpg, .406 FG, .365 3-pt.

Small sample size, but there’s much to like in this young power player with the beginnings of an effective 3-pointer. He’s still raw with a great deal of development ahead. Has the best 3-pointer celebration in the league with that bow-dab.

COACHING: A

Stevens continues to face a challenge finding ways to coax more offensive flow out of his team, and the Celtics are indeed still limited with the ball. But to have the team in this position despite the loss of Hayward is remarkable.

MANAGEMENT: B

It all goes back to Hayward. Ainge’s vision is incomplete until the multi-skilled shooter and playmaker returns. The signings of Theis and Larkin were aces. Once he gets acclimated, Monroe should give a boost to second unit scoring and rebounding. The failure to land a shooter at the trade deadline — Tyreke Evans would have been a great rental, even for one of the Celtics’ own first-rounders — could hurt the rest of the way. They’re still watching the buyout market.